The breakdown voltage and the operating resistance (On resistance or Rdson) are important characteristics of a power semiconductor device. The Rdson of a conventional power device and the breakdown voltage of a power semiconductor device are inversely proportional. That is, the improvement in one adversely affects the other. To overcome this problem, U.S. Pat. No. 5,998,833 proposes a trench type power semiconductor in which buried electrodes are disposed within the same trench as the gate electrodes in order deplete the common conduction region under reverse voltage conditions, whereby the breakdown voltage of the device is improved. As a result, the resistivity of the common conduction region can be improved without an adverse affect on the breakdown voltage of the device.
The buried electrodes shown in U.S. patent No. '833 are electrically connected to the source contact of the device. The '833 patent, however, does not illustrate a structure for connection the source contact to the buried electrode.